Method for heating with superheated steam



Dec. 8, 1925- B. BROIDO METHOD FOR HEATING WITH SUPERHEATED STEAM Filed April 13, 1923 IN VEN TOR.

A TTORNE Y.

Patented Dec. 8, 1925.

UNITED STATES PATENT OFFICE.

BENJAMIN BROIDO, OF NEW YORK, N. Y., ASSIGNOR TO THE SUI'ERHEATER COM- PANY, OF NEW YORK, N. Y.

METHOD FOR HEATING WITH SUPERHEATED STEAM.

Application filed April 13, 1923. Serial No. 631,945.

steam. This steam may be of any desired 7 pressure and may come from any desired or convenient source. Thus it may come directly from the superheater of a boiler especially provided for the purpose, it may be steam extracted from an intermediate stage of a high pressure engine or turbine, possessing some degree of superheat and being re-superheated if necessary, or it may be low pressure exhaust steam which has been re-superheated to the. degree desired for heating purposes. The object of the invention is to provide apparatus and means for effecting the heating more economically than has been heretofore done and with apparatus which would be less expensive than hitherto used.

The invention is shown by way of illustration in the accompanying single sheet of drawings in which the single figure shows an installation deriving its steam from a boiler. The figure is more or less 'diagranr matic and is in sectional elevation.

The boiler shown comprises ahousing 1, water tubes 2, and a steam-and-water drum 3. The type or construction of the boiler plays no part whatever in my invention and in fact, as above mentioned, the steam used in my invention may be derived from some other source. It is, therefore, thought unnecessary to illustrate the boiler in any greater detail.

The steam is superheated in the superheater 4; and from there is carried by pipe 5, main 6, and pipe 7 to the heating coil or radiator 8 locatedin the kiln 9. The radiator 8 comprises headers 10 and 11 to which serpentine or coils of other shape are secured. It will be understood that the number, shape and length of these coils is a matter dependent upon conditions such as the degree of superheat imparted to the steam, the heat which it is desired to attain in the kiln, etc. An important polnt as. will appear presently is the question of steam area in the elements of the radiator.

I have observed that even when superheated steam is used in coils suclr asdescribed the wall temperature of the coiled elements of the radiator is not that of the superheated steam inside of the coils, nor nearly such temperature, but more nearly approximate that of saturated steam of the pressure prevailing on the inside of the coils. The reason for this has heretofore been obscure and it has not been feasible to obtain wall temperatures of the coils higher than those referred to. I have'discovered why only such lower temperatures prevail and my present invention provides for a method and an apparatus for obtaining a wall temperature in the proximity of that of the superheated steam.

lVhen steam, even though superheated, is first introduced into cold coils, a certain amount of initial condensation takes place on the interior walls of the coils, and the water of condensation is ordinarily removed by some form of drainage trap; but is is obvious that drainage alone will not remove the thin capillary film of moisture adhering to the inner wall of the coil.

It is an establishedfact that under certain conditions water will remain as Water in the continued presence of superheated steam,

and I have ascertained that when superheated steam 1s stationary or flows at ,velocities ordinarily employed through a coil such as that described the interior surface of the coil is wet and it is to this'circumstance that I ascribe the fact that the wall itself has a temperature only approximating that of saturated steam of the corresponding pressure. My infiention contemplates removing all the moistureon the coil ,walls due to initial condensation, preventing the formation of any further condensation on the walls during the normal operation of the radiator, and getting the superheated steam into direct contact with the wall. I do this by circulating the steam through the-coil at a very high velocity, as I have found that when the steam exceeds a certain so-ealled critical velocity, it re-evaporates any moisture on the interior walls of the coil and maintains them in a dry state as long as this velocity is maintained. It is particularly to be noted in this connection thatthe test as to Whether or not the proper ve-' rri locity' has been attained is not the quality or temperature of the steam emerging from the coil, as superheated steammay be delivered therefrom while the coil walls remain in a wet condition. The true test is the temperature of the coils. As long as the coil remains at or near the temperature of saturated steam at the pressure used, it is evident that the critical velocity has not been attained and the interior walls of the coil are wet but if the coil is at the temperature approximately that of the superheated steam passing through it, it indicates that the critical velocity has been reached or passed and that the coil walls are in a dry state, permitting direct .and intimate contact between the coil and the steam passing therethrought The convenientway of obtaining such high velocities is by making the coils comparatively small in diameter, keepin the total cross sectional area of all the coils low. It"'is for this reason that in the illustration the coils are shown rather small. Obviously other ways can be used to impart this desired higher velocity, such, as placing a spiral vbaflie in the tube, or by resorting to forced circulation. The-meansfirst mentioned, that is, using small diameter tubes, is'to be understood to be only illustrative. v

With an arrangement such as described the superheated steam remainsin intimate confixed one, nor one exceeding a certain minimum, but will vary from case to case depending upon the degree of superheat, the temperature outside of the .device, and other factors dependent upon the characteristics of the individual installation.

Obviously the invention can be carried out with apparatus varying considerably from that herein described.

that I claim is:

' 1. The process of heating with steam, comprising superheating the steam and passing it through the heating apparatus at such velocity that the walls of said apparatus in contact with said steam are maintained in a dry state during the normal operation of the process.

2. The process of heating with steam, com

prising superheating the steam and passing it through the heating, apparatus at such velocity that the capillary film of moisture resulting from the initial condensation on the walls of said apparatus in contact with said steam is removed by evaporation, and said walls are thereafter maintained in a dry state during the normal operation of the process. 1

3.- The processot' heating with steam comprising the steps of taking steam from a source of supply, superheating it and abstracting from it a portion of its heat of superheat under such conditions that it does not',come into contact/with moist surfaces duringnormal operation of the process.

' 41. The process of heating with steam comprising the steps of tak ng steam from a source of supply, superheatmg 1t and abstracting from it a portion of its heat of superheat under such conditions that the temperature of the surfaces to which it gives upbeat during normal operation is maintained at substantially the temperature of the superheated steam.

BENJAMIN BROIDO. 

